The Black family

The Black family was started some time in the 18th century and the two people that started it remain unknown.

However, we do know their children: Phineas Nigellus, Elladora, Iola, and Sirius the first. Iola went on to marry Bob Hitchens.  While Phineas Nigellus married Ursula Flint, having five children, Cygnus the second, Belvina, Phineas, Sirius the second, and Arcturus the second.
Cygnus married someone named Violetta Bulstrode, whom later had four kids named Marius, Pollux, Dorea, and Cassiopeia.

Dorea had a kid who's name is unknown with Charlus Potter (one of Harry Potter's ancestors).

Pollux and Irma  Crabbe had three children, Alphard, Walburga, and Cygnus the third.

Walburga had what you know as Regulus the second and Sirius the third with Orion Black. 
Cygnus married Druella Rosier and three children were born: Bellatrix, Narcissa, and Andromeda. 
Andromeda married Ted Tonks, making Nymphadora Tonks. And she married Remus Lupin and they together, made Ted Lupin.

Bellatrix, on the other hand married two people, Rodolphus Lestrange and Tom Riddle. She gave birth to Delphini a little while before the battle of hogwarts.

And Narcissa also tried to keep the line of purebloods going by marrying Lucius Malfoy and having Draco Malfoy, whom later married Astoria Greengrass and had Scorpius Malfoy. 
We should head back to Belvina Black because she married Herbert Burke, and had three kids who's names are unknown.

But don't forget about Sirius the first who married Hesper Black and had three children, Regulus the first, Lycarus, and Arcturus the third. Arcturus married Melania Macmillian and they had two kids of their own: Lucretia and Orion (the father of Sirius the third and Regulus the second). Lucretia married Ignatius Prewett and had zero children.

Once again, we will go up to Arcturus the second. Who married Cysandra Black and had Callidora, Cedrella, and Charis.

Charus and somebody named Casper Crouch had three kids. Two are unknown and Oone was Bartemus senior, who married a person with an unknown name, having Bartemus Crouch Jr.

Callidora married Harfang Longbottom and had two unknown kids. 
And finally, Cedrella, who married Septimus Weasley, which leads us two the Weasley Family